Solenoid valves have been conventionally used to control the flow rate of a fluid by using a solenoid to control valve activation. A conventional solenoid valve has a magnetic sensor, which is typically a Hall effect sensor, that effectively senses movement of a component and thus provides positional information for a moving component positioned in high pressure fluid in a fluid delivery device.
The Hall effect sensor used in motion sensing can offer enhanced reliability in extreme environments. A coil contained in the solenoid valve produces an electromagnetic field that may interfere with the accurate performances of the Hall effect sensor, but the prior art, such as Fukano et al., U.S. Pat. No. 6,666,429, does not have any protective mechanism to prevent external electromagnetic fields from interfering with the Hall effect sensor.
It is an object of the invention to provide a shield made of an appropriate protective material so that the performance characteristics of the Hall effect sensor are not compromised by external electromagnetic fields created by the solenoid coil.